Over the years considerable work has been devoted to additives for controlling (preventing or reducing) deposit formation in the fuel induction systems of spark-ignition internal combustion engines. In particular, additives that can effectively control intake valve deposits represent the focal point of considerable research activities in the field and despite these efforts, further improvements are desired. Among relatively recent efforts along these lines is U.S. Pat. No. 5,242,469 and published Canadian patent application 2,089,833.
The additive systems described in U.S. Pat. No. 5,242,469 comprise an ester and at least one dispersant component chosen from certain monosuccinimides, bis(succinimides), polyolefin polyamines, and benzylamine derivatives. The benzylamine derivatives appear to be Mannich-type detergents*. These additive combinations may further contain a polyoxyalkylene glycol or derivative thereof having a molecular weight of 500-5000, preferably 1000-3000. Also, a specified type of lubricating oil fraction may be included in the additive mixture. The polyoxyalkylene glycol derivatives referred to in the text of the patent include the ethers, esters and ether aminoacid esters of the polyoxyalkylene glycol. FNT *According to the patent the hydroxybenzyl amine derivatives are made by alkylating a hydroxybenzyl amine which in turn presumably would be formed by a Mannich reaction among phenol, formaldehyde and polyamine. The resultant product should be similar, if not identical, to a product made in the more usual sequence of alkylating the phenol and then conducting the Mannich reaction with the resultant alkylated phenol, formaldehyde and a polyamine.
Canadian patent application 2,089,833 bearing a publication date of Aug. 21, 1993 describes a similar additive system. In particular, the gasoline is to contain (a) from 75 to 450 ppmw of a specified group of Mannich base detergents in combination with (b) from 75 to 175 ppmw of an oil-soluble poly(oxyalkylene) alcohol, glycol or polyol or mono or di ether thereof, wherein the weight ratio of (a) to (b) in the mixture is at least 0.43.